1. Field of the Invention
The present invention relates to a plasma etching method, a plasma etching apparatus, a control program, and a computer storage medium for forming a hole and the like in a low dielectric constant insulation film formed of a carbon containing silicon oxide film by a plasma of an etching gas.
2. Description of the Related Art
Recently, in a manufacturing process of a semiconductor device, instead of a SiO2 film as an insulating film, a low dielectric constant insulation film (Low-K film) formed of a carbon-containing silicon oxide film (a SiCOH film) has been used.
As a plasma etching method for forming a hole in the low dielectric constant insulation film formed of a carbon-containing silicon oxide film as mentioned above, for example, a method using an etching gas containing a mixed gas of C4F8/CH2F2/Ar/CO/N2 is known (for example, refer to Japanese Patent Laid-open Application No. 2001-210627).
Further, as anther plasma etching method for forming a hole in the low dielectric constant insulation film formed of a carbon-containing silicon oxide film as mentioned above, a method comprising a main etching using an etching gas consisting of a mixed gas of CH3/N2/Ar, and further over-etching using an etching gas consisting of a mixed gas of C4F6/N2/Ar is known (for example, refer to Japanese Patent Laid-open Application No. 2003-209037).
Incidentally, accompanying with miniaturization of a semiconductor device, diameters of a contact hole, a via hole and the likes have a tendency to be smaller and aspect ratios thereof have also a tendency to be increased. For example, it is required to have a hole diameter of 150 nm or less and an aspect ratio of 3 or more. To cope with the above requirements, as a photo resist for forming a mask at the etching, an ArF resist which uses an ArF excimer laser (wave length 193 nm) as an exposure light source has been used.
However, as a result of extensive studies, the inventor has found that when the low dielectric constant insulation film of the carbon-containing silicon oxide film is etched by using the ArF resist and the etching gas mentioned above, the selection ratio of resist is lowered, many vertical lines are formed in the inner wall of the hole, and a problem that the surface of inner wall is roughened is occurred.